An organic light-emitting diode display (for example AMOLED) is one of the research hotpots for a current flat-panel display device. As compared with a liquid crystal display device, the OLED has such advantages as low power consumption, low production cost, autoluminescence, wide viewing angle and rapid response. Recently, the OLED has begun to replace a traditional liquid crystal display (LCD) in such fields as mobile phones, PDAs and digital cameras. The design of a pixel driving circuit is a core technique of the AMOLED display device, and thus it is of important research significance.
Different from a TFT-LCD which controls the brightness with a stable voltage, the OLED is driven to emit light with a stable current. Due to a manufacturing process and the aging of elements, a threshold voltage (Vth) of a driving TFT for each pixel point will be drifted, which results in a change of the current passing through the OLED for each pixel point along with a change of the threshold voltage. As a result, the display brightness is uneven, and thereby a display effect of an entire image will be adversely affected.
Currently, an in-cell touch technology has been applied to the LCD, and it commonly includes a capacitive in-cell touch technology. However, as the most difficult problem to be solved in the capacitive in-cell touch technology, there is signal interference, i.e., there is a considerable parasitic capacitance between a touch electrode and an electrode desired for the operation of the LCD. As a result, it is very difficult to prevent display characteristics of the LCD itself from being adversely affected while ensuring that a touch signal is collected successfully.
Hence, a combination of the capacitive in-cell touch technology with the AMOLED will be a future trend of the display technology.